Helicopters have now become entrenched as an integral part of the weapons system carried by destroyers and frigates in anti-submarine search and strike capacity. Invariably, landings and take-offs of these helicopters from vessels must be made in moderate to severe turbulence and once on the deck, the helicopter must be quickly secured and stored for protection from the environment.
Two such helicopters are the Sea Hawk (trade mark) and Sea King (trade mark).
The Sea King, a 20,000 pound helicopter includes a conventional undercarriage comprising a rear wheel free wheeling through 360 degrees and a pair of spaced dual wheel units on either side, and near the nose of the helicopter. For recovery, employing the RAST System (Recovery Assist Secure and Traverse System) for helicopter recovery, the Sea King mounts externally on its underside an airborne messenger winch intermediate the rear wheel and a pair of dual wheel units. The messenger winch holds a light duty cable with a messenger link and lock assembly for the flydown cable. When the flydown cable from the self-centering and self-balancing sliding bell mouth is secured to the messenger winch, a constant tension is maintained in the cable until the helicopter is landed safely. Once the helicopter has landed an increased tension is applied automatically by the electric tension winch for securing the helicopter.
After landing, the Sea King helicopter is moved into the hangar.
In Canadian Letters Patent No. 781,808 a helicopter rapid securing system is disclosed employing a constant tension winch used to maintain the tension in the cable securing the airborne helicopter to the ship and a frame surrounding the fairlead through which the cable extends below deck, supporting two parallel arresting rails for firing towards one another from opposite sides to the frame to capture the probe of the helicopter securing the cable to the helicopter when the helicopter has landed to secure the helicopter to the deck. Thereafter, the frame is withdrawn along the track traversing the Sea King helicopter to the hangar.
While the method described in Canada Letters Patent No. 781,808 is fast and reliable, it is also very expensive. However, because the capture and traverse functions are carried out by the same structure involved in helicopter haul-down, it is also safe. When the helicopter lands, not only is it secured to the ship's deck, it is also simultaneously secured to the traverser used for traversing it to the hangar. However, the said structure is complex and costly both to buy and maintain. Additionally, because the arresting beams are fired from opposite sides of the frame to engage the probe within the confines of the frame, the landing area is fixed in size.
U.S. Pat. No. 4,123,020 teaches an arm carrying a pair of digits arranged to move on a track by means of a right and left screw jack which is driven by a hydraulic motor. Each of the digits carries clamping jaws to secure the stud of the VTOL between the digits. This structure is not practical. Neither is the structure shown in the U.S. Pat. No. 4,420,132. The scissors action of the arms may damage the probes.
U.S. Pat. No. 3,659,813 discloses the use of a trolley to which a helicopter is secured for traversing once on the deck of a ship. The trolley is displaceable along a worm gear mounted on the cross strut driven in a linear path by a drive mechanism. However, this system cannot be used to rapidly secure the helicopter on landing. It is merely a type of traversing device.
In Canadian Patent Application No. 494,567 there is disclosed a helicopter rapid securing and traversing system and securing means for securing a helicopter upon landing on the deck of a ship for subsequently traversing it from its landing position, said system comprising a housing reciprocal from a position remote the landing area to a position adjacent the landing area of the helicopter (for example, in a track) the housing carrying a shock absorber and sensing means extending across the housing for contacting a probe or other projection (such as a wind housing) extending from the helicopter on the exterior of the helicopter when the helicopter has landed on the deck and the housing is brought to engage the probe or other projection, the shock absorbing bar and sensing means for slowing and stopping the movement of the housing when the probe or projection is engaged and for cushioning the engagement (as for example, to engage a switch turning off the electrical power to a motor used to move the housing to the helicopter landing area) and for sensing the position of the probe or projection, the sensing means in one embodiment being incorporated with the shock absorber in one structure, and in another embodiment being separate from the shock absorber and being a sensing bar which extends parallel to the carrier and shock absorber and being positioned along the centre line of a laterally opening mouth of securing means for securing to the probe or projection carried by a carrier on the housing in either case to stop the probe in a position along the centre line of the mouth, means for reciprocating the housing towards and away from the landing area, a carrier on the housing and carrying securing means thereon for securing the housing to the probe or projection on the helicopter, (in a preferred embodiment being a lead screw extending across the housing, and in another embodiment, either a hydraulically or electrically driven chain), the securing means being normally secured at one side of the housing on the carrier and being moved laterally along the carrier across the housing when the carrier is activated to capture the probe or projection, the securing means carrying a laterally opening mouth opening in the direction towards the probe, and means to operate the carrier (in one embodiment where the carrier for the securing means comprises a lead screw, the means to operate the lead screw comprises a high speed electric motor for turning the lead screw to move the securing means therealong by reciprocal means on the securing means engaging the lead screw and a slow speed high torque electric motor for turning the lead screw once the probe is grasped by the securing means, means to deactivate the high speed motor when the probe is grasped by the securing means but not lock the motor, permitting it to free wheel and a clutch for connecting the slow speed high torque electric motor to the lead screw when the high speed motor is deactivated), whereby when the probe or projection engages the shock absorber and sensing means, the impact of the probe is cushioned and the position of the probe or projection is sensed relative to the mouth of the securing means whereby when the probe is sensed as positioned in line with the mouth of the securing means, the carrier moves the securing means to grasp and secure the probe or projection and when the probe is sensed not to be appropriately positioned, the system is activated to cause the system to be appropriately positioned relative to the probe.
In one embodiment the helicopter rapid securing and traversing system provided for securing the helicopter upon landing on the deck of the ship and for subsequently traversing it from its landing position, comprises:
a housing reciprocal from a position remote the landing area to a position adjacent the landing area of a helicopter (for example, in a track) carrying a shock absorbing bar extending across the housing for engaging a probe or other projection (such as a winch housing) extending from the helicopter on the exterior of the helicopter when the helicopter has landed on the deck of the ship and the housing is brought to engage the probe or other projection, the shock absorbing bar for cushioning the impact of the probe or other projection when the probe or other projection engages the shock absorbing bar carried by the housing to slow and stop the movement of the housing (as for example, to engage a switch turning off the electrical power to a motor used to move the housing to the helicopter landing area);
means for reciprocating the housing towards and away from the landing area;
a carrier on the housing extending parallel to the shock absorbing bar but closer to the housing than the shock absorbing bar (in a preferred embodiment being a lead screw extending across the housing, and in another embodiment, either a hydraulically driven or electrically driven chain drive);
the carrier carrying securing means thereon for securing the housing to the probe or other projection on the helicopter, the securing means being normally secured to one side of the housing on the carrier for being moved laterally from one side of the housing towards the other side when the carrier is activated to move laterally across the housing, the capture the probe or projection;
the securing means carrying a laterally opening mouth opening in the direction towards the probe;
sensing means for sensing the position of the probe relative to the mouth of the securing means whereby when the probe is sensed to be positioned in line with the mouth of the securing means the housing is stopped so that when the securing means is moved by the carrier, the securing means will grasp and secure the probe or projection and when the sensing means senses the probe is not appropriately positioned (as for example, when the helicopter and thus the probe has moved away), the system is activated to cause the system to be appropriately positioned relative to the probe), (the sensing means in one embodiment being a sensing bar which extends parallel to the carrier and shock absorbing bar and is positioned closer to the housing than the shock absorbing bar and being positioned along the centre line of the laterally opening mouth of the securing means and in one embodiment the sensing means being incorporated with the shock absorbing bar in one structure, in both embodiments to stop the system in a position wherein the probe is along the centre line of the mouth, for example, by depressing and causing a switch to be engaged, stopping movement of the housing when the housing is slowed down and stopped when the probe or other projection is engaged permitting the carrier to move the securing means laterally across the housing to capture the probe); means to operate the carrier (in one embodiment where the carrier for the securing means comprises a lead screw, the means to operate the lead screw comprises a high speed electric motor for turning the lead screw to move the securing means therealong by reciprocal means on the securing means engaging the lead screw and a slow speed high torque electric motor for turning the lead screw once the probe is grasped by the securing means, means to deactivate the high speed motor when the probe is grasped by the securing means but not lock the motor permitting it to free wheel, and a clutch for connecting the slow speed high torque electric motor to the lead screw when the high speed motor is deactivated.
It is also now widely accepted that RPVs (Remotely Piloted Vehicles) have the potential to fill several significant military roles. The majority of the effort to date has addressed land based RPV systems and very little has been done on the development of ship based systems.
Use of RPVs in the Naval environment [Shipboard Launch and Recovery system (SLAR) and the RPV] adds a number of new challenges, for the proposed short range RPV, in particular operating from frigate sized and smaller ships means taking off from, and landing on, an unstable moving deck, with severe airwake turbulence from the superstructure and very tight space constraints both during operation and stowage. A strong trend is already emerging in favour of RPVs with a VTOL capability for the maritime role because of the demonstrated difficulties of landing a fixed wing air vehicle on even relatively large and stable ships' decks. On land, the VTOL RPV requires little or no launch and recovery support and hence this area of development has been largely ignored. In the shipboard application this is not true.
Requirements for launch, recovery and handling systems are only just starting to be formulated. However, a consensus is emerging that RPVs should be capable of operating off frigate sized ships in at least sea state 3 with 10.degree. roll, 3.degree. pitch (typically) and ideally up to sea state 5 with 30.degree. roll, 10.degree. pitch compatible with current United States and Canadian Navy helicopter operational limits.
Initial RPV placements will probably be on ships which are already operating with one or more helicopters; however, the system must also be adaptable to smaller, non-flight deck equipment ships. On existing flight decks, the goal must be to complement the helicopter capability rather than to displace it. To this extent, the RPV must operate on a non-interference basis and share the already cramped quarters in the hangar. The RPV system must require minimal additional crew members for operation or maintenance, as well as minimizing any additional skill levels.
There are five (5) distinct phases in the launch, recovery and handling of RPVs from small ships; recovery assistance, securing, traversing or deck handling, stowage and of course launch.
Recovery assistance requirements will, to a great extent, depend on the stability characteristics of a number of elements - the UMA, the operating envelope limits and the ship motion and associated airwake turbulence.
A very stable and controllablle air vehicle operating in relatively calm conditions may not require any specific recovery assistance other than that provided by the normal RPV operator.
In higher sea states and/or with a less stable air vehicle the operator workload will increase dramatically to the point where some form of recovery assistance becomes mandatory. The Naval helicopter pilot has difficulties under such conditions. The situation is even worse for an RPV operator for several reasons. Although the operator can maintain good visual contact with the RPV, he lacks the "seat of the pants" acceleration feedback. He also has difficulty in judging RPV position since he is, most likely, looking up at the RPV and has no references in the background to provide visual cues as to the RPV's position relative to the ship. Finally, the RPV being a much smaller craft, is far more susceptible to wind shears and high frequency turbulence in the airwake behind the ship's hangar or other superstructure.
Whatever form of recovery assistance is provided, the goal must be to eliminate flight deck personnel during launch and recovery operations.
Once landed, the RPV needs to be secured as quickly as possible; ideally before the end of the quiescent period to avoid it sliding across the deck (or worse still, toppling) during the next roll or pitch cycle.
In U.S. Pat. No. 4,890,802, a landing and securing platform is provided for the landing of an RPV thereon and which can be released from the landing point to become a dolly which may be maneuvered normally to and from a hangar. Alternatively, the platform can be secured by cables and winched across the flight deck. Ideally to preserve maximum security, the platform is guided along and restrained by some form of track or rail. This track could be either an existing track or a separate lightweight surface mounted track. Any track installation of course must not interfere with helicopter operations or be subject to damage during vertical replenishment. If an existing track is used, the platform should have a means of disengagement from the track inside the hangar, and preferably an auxiliary track to take it to its stowage area.
In the said application, a capturing, securing and traversing system for an RPV is provided suitable for use on shipboard, the system comprising a pair of grids overlying one another, the lower grid moveable (rotatable or translation) relative to the upper grid, each grid comprising rigid cables or wires crossing one another for receiving a probe therethrough, the RPV having a lower support (for example a plurality of legs or a ring) comprising a plurality of broad pads at the lower end thereof to each sit on the upper grid without penetrating through the grid, the undersurface of pads carrying a downwardly extending probe (or finger) of a length sufficient to pass through both grids, preferably the lower end carrying means (for example a larger or bulbous end) whereby when the probe passes through the two grids, the probe becomes clamped by the grids after the lower grid has been moved (either by rotation or translation) and the probes are precluded from being withdrawn (for example by precluding the bulbous or larger ends of the probes (or fingers) from passing through the spaces between rigid cables or wires of the upper and lower grids engaging both sides of the probes (or fingers)).
There is also provided a capturing, securing and traversing system for an RPV suitable for use on shipboard, the system comprising a grid comprising rigid cables or wires crossing one another for receiving a probe therethrough, the RPV having a lower support (for example a plurality of legs or a ring) comprising a plurality of broad pads at the lower end thereof to each sit on the grid without penetrating the grid, the undersurface of the pads carrying a downwardly extending probe (or finger) of a length sufficient to pass through both grids, the lower end of the probes each carrying means to temporarily expand the lower end of probes to preclude the withdrawal thereof from the grids. The lower end of the probe may carry a plurality of wings retractable into the body but upon being extended, extends transverse the length of the probe to preclude probe withdrawal.
There is also provided a capturing, securing and traversing system for an RPV suitable for use on shipboard, the system comprising a platform comprising a plurality of slots (preferably extending radially towards the center of the platform), each slot carrying a vertically extending arm movable in the slot carrying means (for example a laterally extending finger) for securing to the support (for example bottom ring or legs of the RPV) when moved radially towards the center and means for moving the arms in the slots (for example a lead screw operated by a motor and gears). It will be appreciated that by moving the arms after the means on the arms engage and secure the support (for example the legs or ring) to the system, the further movement of the arms can cause the RPV to be moved to center the RPV on the platform. For example, if each of the arms is operated by lead screws and if the lead screws are synchronized in their operation, the RPV may be moved on the platform (for example centered). In one embodiment the means may comprise laterally extending flanges which may extend over the support (for example ring) or clamp the support (ring or legs).
The laterally extending fingers may be secured to raised arms which can be retracted into and extended from the sides of the platform. Thus where the RPV is supported on a pair of parallel skids, the arms may be extended laterally from the platform prior to the landing of the RPV and after the RPV has landed, the arms are retracted causing the arms to be retracted with the ringers overlying the skids.
Each of the above systems (for example grids and platforms) may be mounted for movement on the ship deck. In this regard, each of the systems may be pinned to a cable and may be traversed on the ship deck (for example either in a surface mounted track or in a track permanently constructed in the deck).
To assist in the landing of helicopters, video cameras (part of video system) have been proposed to be mounted on the face of the hangars in which the helicopters are to be stored and reflectors provided on the helicopter at predetermined positions for directing light to be picked up by the cameras for determining the helicopter's position.
These proposals suffer from a number of deficiencies. By mounting the cameras as proposed above, reflections of sunlight or illuminating lights from the front windshield and other glass windows and the body of the aircraft will be picked up by the cameras and transferred to the remainder of the video system causing confusion when the signal(s) received is (are) used to determine the aircraft's position.
Additionally, because the cameras are mounted remote from the landing position of the aircraft, as the aircraft descends to its landing position, the error never approaches "0" in the calculations.
It is therefore an object of this invention to provide improved systems and components therefor suitable for use in landing aircraft on the ship deck.
It is a further object of this invention to provide improved landing and securing systems suitable for use for landing and securing an aircraft landing on the deck of a ship.
It is a further object of the invention to provide improved components suitable for use with such systems.
Further and other objects of the invention will be realized by those skilled in the art from the following summary of the invention and detailed description of embodiments thereof.